Commit ffed24ef authored by Jiri Olsa's avatar Jiri Olsa Committed by Daniel Borkmann
Browse files

selftests/bpf: Add test for early update in prog_array_map_poke_run 



Adding test that tries to trigger the BUG_IN during early map update
in prog_array_map_poke_run function.

The idea is to share prog array map between thread that constantly
updates it and another one loading a program that uses that prog
array.

Eventually we will hit a place where the program is ok to be updated
(poke->tailcall_target_stable check) but the address is still not
registered in kallsyms, so the bpf_arch_text_poke returns -EINVAL
and cause imbalance for the next tail call update check, which will
fail with -EBUSY in bpf_arch_text_poke as described in previous fix.

Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/bpf/20231206083041.1306660-3-jolsa@kernel.org
parent 4b7de801

tools/testing/selftests/bpf/prog_tests/tailcalls.c

+84 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <unistd.h>

#include <test_progs.h>

#include <network_helpers.h>

#include "tailcall_poke.skel.h"





/* test_tailcall_1 checks basic functionality by patching multiple locations

 * in a single program for a single tail call slot with nop->jmp, jmp->nop
@@ -1105,6 +1108,85 @@ static void test_tailcall_bpf2bpf_fentry_entry(void) 
	bpf_object__close(tgt_obj);

}



#define JMP_TABLE "/sys/fs/bpf/jmp_table"



static int poke_thread_exit;



static void *poke_update(void *arg)

{

	__u32 zero = 0, prog1_fd, prog2_fd, map_fd;

	struct tailcall_poke *call = arg;



	map_fd = bpf_map__fd(call->maps.jmp_table);

	prog1_fd = bpf_program__fd(call->progs.call1);

	prog2_fd = bpf_program__fd(call->progs.call2);



	while (!poke_thread_exit) {

		bpf_map_update_elem(map_fd, &zero, &prog1_fd, BPF_ANY);

		bpf_map_update_elem(map_fd, &zero, &prog2_fd, BPF_ANY);

	}



	return NULL;

}



/*

 * We are trying to hit prog array update during another program load

 * that shares the same prog array map.

 *

 * For that we share the jmp_table map between two skeleton instances

 * by pinning the jmp_table to same path. Then first skeleton instance

 * periodically updates jmp_table in 'poke update' thread while we load

 * the second skeleton instance in the main thread.

 */

static void test_tailcall_poke(void)

{

	struct tailcall_poke *call, *test;

	int err, cnt = 10;

	pthread_t thread;



	unlink(JMP_TABLE);



	call = tailcall_poke__open_and_load();

	if (!ASSERT_OK_PTR(call, "tailcall_poke__open"))

		return;



	err = bpf_map__pin(call->maps.jmp_table, JMP_TABLE);

	if (!ASSERT_OK(err, "bpf_map__pin"))

		goto out;



	err = pthread_create(&thread, NULL, poke_update, call);

	if (!ASSERT_OK(err, "new toggler"))

		goto out;



	while (cnt--) {

		test = tailcall_poke__open();

		if (!ASSERT_OK_PTR(test, "tailcall_poke__open"))

			break;



		err = bpf_map__set_pin_path(test->maps.jmp_table, JMP_TABLE);

		if (!ASSERT_OK(err, "bpf_map__pin")) {

			tailcall_poke__destroy(test);

			break;

		}



		bpf_program__set_autoload(test->progs.test, true);

		bpf_program__set_autoload(test->progs.call1, false);

		bpf_program__set_autoload(test->progs.call2, false);



		err = tailcall_poke__load(test);

		tailcall_poke__destroy(test);

		if (!ASSERT_OK(err, "tailcall_poke__load"))

			break;

	}



	poke_thread_exit = 1;

	ASSERT_OK(pthread_join(thread, NULL), "pthread_join");



out:

	bpf_map__unpin(call->maps.jmp_table, JMP_TABLE);

	tailcall_poke__destroy(call);

}



void test_tailcalls(void)

{

	if (test__start_subtest("tailcall_1"))
@@ -1139,4 +1221,6 @@ void test_tailcalls(void) 
		test_tailcall_bpf2bpf_fentry_fexit();

	if (test__start_subtest("tailcall_bpf2bpf_fentry_entry"))

		test_tailcall_bpf2bpf_fentry_entry();

	if (test__start_subtest("tailcall_poke"))

		test_tailcall_poke();

}

tools/testing/selftests/bpf/progs/tailcall_poke.c

0 → 100644
+32 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <linux/bpf.h>

#include <bpf/bpf_helpers.h>

#include <bpf/bpf_tracing.h>



char _license[] SEC("license") = "GPL";



struct {

	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);

	__uint(max_entries, 1);

	__uint(key_size, sizeof(__u32));

	__uint(value_size, sizeof(__u32));

} jmp_table SEC(".maps");



SEC("?fentry/bpf_fentry_test1")

int BPF_PROG(test, int a)

{

	bpf_tail_call_static(ctx, &jmp_table, 0);

	return 0;

}



SEC("fentry/bpf_fentry_test1")

int BPF_PROG(call1, int a)

{

	return 0;

}



SEC("fentry/bpf_fentry_test1")

int BPF_PROG(call2, int a)

{

	return 0;

}